A conventional liquid crystal display (LCD) apparatus, for example, disclosed in JP-H11-38384A, includes a liquid crystal panel, a backlight for illuminating the liquid crystal panel, a circuit board having an electrical circuit for driving the liquid crystal panel. The liquid crystal panel, the backlight, and the circuit board are stacked in that order and housed in a case.
In such a conventional LCD apparatus, a heater heats the liquid crystal panel to its desired operating temperature, thereby increasing the speed of response of the liquid crystal panel. The circuit board includes many circuit elements such as a transistor, diode, and the like. Some of these circuit elements (e.g., a power control element for controlling the backlight) generate heat. Therefore, temperature of the conventional LCD apparatus is higher than ambient temperature during its operation.
Some of these circuit elements (e.g., a central processing unit (CPU) for controlling the liquid crystal panel) have a relatively low maximum operating temperature. The circuit elements having the relatively low maximum operating temperatures need to be maintained below the respective maximum operating temperatures during the operation of the conventional LCD apparatus.
The conventional LCD apparatus is mounted to a vehicle such that the liquid crystal panel faces horizontally toward a driver. Therefore, the conventional LCD apparatus is approximately vertically mounted to the vehicle, and accordingly the circuit board is approximately vertically positioned during normal use of the conventional LCD apparatus.
Since the temperature of the conventional LCD apparatus is higher than the ambient temperature during its operation, air flows upward inside the conventional LCD apparatus due to natural convection. The upward flow of air cools the circuit elements mounted on the circuit board.
Some of the circuit elements, for example, a capacitor, are relatively tall. In other words, a distance from a mounting surface of the circuit board to a top surface of some of the circuit elements is relatively long. The number of the tall circuit elements is large and the tall circuit elements obstruct the upward flow of air.
FIG. 7 shows a circuit board 200 as an example of the circuit board of the conventional LCD apparatus. Capacitors 9, 10, a central processing unit (CPU) 11, and electronic elements 12 are mounted on the circuit board 200. FIG. 8 shows the circuit board 200 viewed from a vertical direction indicated by an arrow VIII of FIG. 7. As can be seen from FIG. 8, the capacitors 9, 10 are relatively tall. The conventional LCD apparatus is mounted to the vehicle in the vertical direction, and accordingly the circuit board 200 is positioned in the vertical direction during normal use of the conventional LCD apparatus.
As shown in FIG. 7, the capacitors 9, 10 as the tall circuit elements are arranged all over the circuit board 200 because the capacitors 9, 10 are arranged only in terms of their function as an electrical circuit. As shown in FIG. 8, therefore, there is very little space area along the mounting surface of the circuit board 200. As a result, the amount of the upward flow of air is reduced and the circuit elements mounted on the circuit board 200 cannot be maintained below the maximum operating temperature during the operation of the conventional LCD apparatus.
Increasing a distance between the case and the capacitors 9, 10 may produce the upward flow of air enough to cool the circuits elements mounted on the circuit board 200. However, recently, there has been an increase in demand for a LCD apparatus having reduced size, in particular, reduced thickness. Therefore, it is difficult to increase the distance between the case and the capacitors 9, 10.